Japanese options if the Pacific Fleet stayed on the US West Coast

How would Japanese plans change if the United States had not moved the Pacific Fleet to Pearl Harbor?

Japan probably would not attack Pearl Harbor and would more likely concentrate on the Philippines, since a major strike on San Diego was logistically unrealistic.

Without the Pacific Fleet at Pearl Harbor, Japan would probably concentrate its opening attack on the Philippines. Supporting a mass carrier force off San Diego would exceed the logistics envisaged for the historical operation, although a much smaller raid is considered conceivable. An I-400-type long-range arrangement is raised as another hypothetical way to reach farther across the Pacific. The chronology of the American move draws disagreement: one participant identifies 1940 as the major shift, while Clarke emphasizes the buildup of Pearl Harbor and the earlier presence of increasingly large forces. He distinguishes Richardson's command of the United States Fleet from the later Pacific Fleet organization and places a command reorganization in January 1940. In that interpretation, the intended concentration had been visible for years, while defensive investment failed to keep pace.